Tensioned cross wire grid having soldered crossing points



Dec. 18, 1962 H. KATZ 3,069,585

TENSIONED qRoss WIRE GRID HAVING SOLDERED CROSSING POINTS Filed Sept.30, 1959 United tates tice 3,069,535 TENSIONED CROSS WERE G HAVINGSOLDERED CROSSKNG POINTS Helrnut Katz, Munich, Germany, assignor toSiemens and Halske Aktiengesellschaft Berlin and Munich, a corporationof Germany Filed Sept. 30, 1959, Ser. No. 843,578 Claims priority,application Germany Oct. 16, 1958 3 Claims. (Cl. 313348) This inventionis concerned with a frame grid of the cross wire type comprising atleast two layers of tensioned parallel wires made of tungsten,molybdenum and the like, positioned superposed so that the wires ofdiiferent layers extend at a desired angle, such wires being solderedtogether at the crossing points and having for this purpose, inter alia,a coating of at least one metal.

Planar frame grids of this kind have been extraordinarily useful in thecase of disk type tubes. Such grids exhibit in operation of thecorresponding tubes in addition of the best mechanical and heatconducting properties negligibly low inductivity and therefore permitoperation with limit frequencies which cannot be reached at all withgrids lacking the punctiform soldering.

For soldering the common crossing points of the grid wires together, itis in the interest of simplification of the operations and for obtainingvery exact grids, generally necessary to provide the wires with asolderable coating, such coating melting upon soldering. However, suchmetal coatings frequently have the drawback that they assume inoperation, by strong heating, be it due to slight spacing from thecathode or to current connected thereto, a considerable temperature atwhich the metallic coatings can vaporize. Accordingly, metals, having arelatively high melting point are used to form the coatings, gold beingan example of such metals. On the other hand, the melting point must notbe so high that the tungsten wire, which is in a tensioned gridsubjected to considerable tensile stress, suifers detrimentalrecrystallization. The art is for these reasons bound to a maximumtemperature which preferably shall not exceed 1000 C.

It is in view of this situation the aim and object of the invention toavoid metals with high vapor pressure, that is, metals which at suchoperating temperatures disturb a vacuum of Torr and less due tovaporization, and to permit nevertheless production of such grids attemperatures below 1000 C.

This object is, in connection with a frame grid of the cross wire typehaving at least two layers of tensioned parallel wires made of tungstenand directly superposed so that the wires of dilferent layers extend ata desired angle, with the wires at the crossing points solderedtogether, and using for the soldering, inter alia, a coating of at leastone metal, according to the invention realized by employing a metalcoating for the grid wires which contains in the range of the crossingpoints in addition to titanium at least one further metal adapted toform with the titanium below about 1000 C. a liquid phase required forthe soldering without exhibiting a disturbing vapor pressure for avacuum of 1( Torr or less.

Particularly suitable for applying this measure in connection withtitanium are the metals copper and nickel, each of which forms withtitanium a liquid phase respectively at 875 C. and 955 C.

The invention will now be explained with reference to the accompanyingdrawing wherein:

FIG. 1 shows in purely schematic manner a frame grid of the tensionedcross wire type according to the invention; and

FIG. 2 illustrates likewise diagrammatically the method of producingsuch a grid with the aid of an interposed foil.

The production of such a grid proceeds from a layer of titanized wiresupon which is wound the second layer of nickel plated or copper platedwires. Upon the titanized layer is moreover placed an annular nickelplated or copper plated tungsten member or ring, such annular memberserving as a carrier for the grid, and the resulting assembly issuitably heated to a temperature such as to produce alloy formationbetween titanium and copper (875 C.) or between titanium and nickel (955C.), respectively, depending upon the given combination of parts. Theliquid phase formed thereby solders the individual components together.

It is understood, of course, that the combinations of components may bemodified as required, especially in view of the grid carrier which issimultaneously soldered into place; for example, a tungsten ringprovided with a titanium coating may be placed upon the copper plated ornickel plated wire layer, as a carrier therefor.

In case it is desired that both wire layers be provided with a titaniumcoating, a foil 2, such as shown in FIG. 2 may be placed between thelayers to serve as an alloying member. There is first formed the wirelayer 1, upon which is placed the foil 2, for example, made of nickel,and such foil is formed by pressure exerted by a suitable tool, forexample, molybdenum wires 3 wound in spaced relationship, so that thefoil 2 is caused to sag at spaces between the wires 1. The second layerof titanized wire 4 is thereupon wound in place. The foil 2 now engagesone wire layer along the generatrix of the cylindrical wire thereofwhile engaging the other layer only at the crossing points. The alloywill be formed at suitable temperature only at these points ofengagement, also for the grid frame 5, thereby effecting the punctiformsoldering.

Depending upon the manner in which the grid is built into the tube, noneof these alloyed points will be facing the cathode side.

The foil parts remaining after the soldering are removed by applying astrong air blast or mild sanding or by suitable cauterizing.

It is understood, of course, that the use of the materials for theindividual parts can also be modified in this method; for example, wirescan be nickel plated and a foil of titanium may be used. The use ofparticular materials will depend upon a given application of the grid.

Changes may be made within the scope and spirit of the appended claimswhich define what is believed to be new and desired to have protected byLetters Patent.

I claim:

1. A frame grid of the tensioned cross wire type comprising a metalliccarrier for supporting at least two directly superposed wire layers eachhaving parallel wires made of material selected from the classconsisting of tungsten, molybdenum and the like, the wires of therespective layers embracing a desired angle and being soldered togetherat the crossing points thereof and also being soldered to said carrierby the aid of a coating of metal provided thereon, said metal coatingcontaining within the areas of said crossing points titanium and atleast one further metal which is adapted to form with the titanium below1000 C. a liquid phase for effecting the soldering and which does nothave a vapor pressure disturbing for a vacuum of 10" Torr and less.

2. A tensioned cross wire type frame grid according to ciaim 1, whereinthe metal coatings of the grid wires contain Within the areas of thecrossing points titanium and in addition thereto a metal selected fromthe class of metals consisting of copper and nickel.

3. A tensioned cross wire type frame grid according to claim 1, whereinthe solder consists of an alloy of titanium and a metal selected fromthe class of metals consisting of copper and nickel.

References Cited in the file of this patent UNITED STATES PATENTS2,304,990 Ewing Dec. 15, 1942 2,577,103 Brian Dec. 4, 1951 2,628,046Hart Feb. 10, 1953 2,661,029 Walsh Dec. 1, 1953 2,874,449 De Rooy et a1.Feb. 24, 1959 FOREIGN PATENTS 1,147,733 France June 11, 1957

1. A FRAME GRID OF THE TENSIONED VCROSS WIRE TYPE COMPRISING A METALLICCARRIER FOR SUPPORTING AT LEAST TWO DIRECTLY SUPERPOSED WIRE LAYERS EACHHAVING PARALLEL WIRES MADE OF MATERIAL SELECTED FROM THE CLASSCONSISTING OF TUNGSTEN, MOLYBDENUM AND THE LIKE, THE WIRES OF THERESPECTIVE LAYERS EMBRACING A DESIRED ANGLE AND BEING SOLDERED TOGETHERAT THE CROSSING POINTS THEREOF AND ALSO BEING SOLDERED TO SAID CARRIERBY THE AID OF A COATING OF METAL PROVIDED THEREON, SAID METAL COATINGCONTAINING WITHIN THE AREAS OF SAID CROSSING POINTS TITANIUM AND ATLEAST ONE FURTHER METAL WHICH IS ADAPTED TO FORM WITH THE TITANIUM BELOW1000*C. A LIQUID PHASE FOR EFFECTING THE SOLDERING AND WHICH DOES NOTHAVE A VAPOR PRESSURE DISTURBING FOR A VACUUM OF 10-6 TORR AND LESS.